1. Technical Field of the Invention
The present invention relates to novel overprint varnishes, and, more especially, to high-performance overprint varnishes comprising composite latices prepared by polymerizing at least one hydrophobic monomer within a matrix solution/dispersion of a particular styrene/maleic anhydride(SMA) resin.
By "overprint varnishes" are intended surface-improvement protective compositions designed to impart to treated surfaces, for example printed or unprinted papers and cardboards, enhanced resistance to external agents and influences, and, in particular, enhanced resistance to friction, moisture, and temperature, and even an improved appearance, for example improved glossiness.
2. Description of the Prior Art
Conventional overprint varnishes comprise aqueous compositions based on composite latices of the styrene/acrylate polymer-styrene/maleic anhydride resin type.
Thus, EP-A-675,177 (Goodrich) describes shell/core latices prepared via the polymerization of mixtures of hydrophobic monomers, such as butyl methacrylate, 2-ethylhexyl acrylate, and styrene in an aqueous styrene/maleic anhydride resin solution, this resin being rendered soluble by salification with a volatile nitrogenous base such as ammonia.